The present disclosure relates to a ratchet mechanism which can transmit a rotational drive force only in one direction and an image forming apparatus including the same.
Conventionally, in an image forming apparatus such as a copying machine, a printer or a facsimile machine, various rotation members are used for units such as a drum unit, a development unit, a fixing unit and a transport unit. In order to rotate such rotation members, it is necessary to transmit a drive force to the individual units from a drive source such as a drive motor, and a plurality of gears are used as a drive transmission mechanism. As such gears, gears made of resin are often used in terms of cost, silence, light weight and the like.
Conventionally, as a mechanism for transmitting only a rotational drive force in one direction, a ratchet mechanism is known which includes a first ratchet gear, a second ratchet gear that can be moved in a direction in which the rotation shaft line of the first ratchet gear is extended and a compression coil spring that applies a force acting toward the first ratchet gear to the second ratchet gear. In the ratchet mechanism described above, on the center portion of the second ratchet gear, a boss is formed which is extended in a direction opposite to the first ratchet gear, and when the ratchet mechanism is assembled, the compression coil spring is held by being attached to the boss. Then, a side plate is pressed onto the compression coil spring from the side opposite to the second ratchet gear, and thus the compression coil spring is sandwiched between the side plate and the second ratchet gear.